Add a new attribute, 'noduplicate'. If a function contains a noduplicate call, the call cannot be duplicated - Jump threading, loop unrolling, loop unswitching, and loop rotation are inhibited if they would duplicate the call.

Similarly inlining of the function is inhibited, if that would duplicate the call (in particular inlining is still allowed when there is only one callsite and the function has internal linkage).

llvm-svn: 170704

1 files changed, 10 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index de6b9952db7..2a04af33d99 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -113,12 +113,13 @@ Pass *llvm::createLoopUnrollPass(int Threshold, int Count, int AllowPartial) {
 
 /// ApproximateLoopSize - Approximate the size of the loop.
 static unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls,
-                                    const DataLayout *TD) {
+                                    bool &NotDuplicatable, const DataLayout *TD) {
   CodeMetrics Metrics;
   for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
        I != E; ++I)
     Metrics.analyzeBasicBlock(*I, TD);
   NumCalls = Metrics.NumInlineCandidates;
+  NotDuplicatable = Metrics.notDuplicatable;
 
   unsigned LoopSize = Metrics.NumInsts;
 
@@ -181,8 +182,15 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
   if (Threshold != NoThreshold) {
     const DataLayout *TD = getAnalysisIfAvailable<DataLayout>();
     unsigned NumInlineCandidates;
-    unsigned LoopSize = ApproximateLoopSize(L, NumInlineCandidates, TD);
+    bool notDuplicatable;
+    unsigned LoopSize = ApproximateLoopSize(L, NumInlineCandidates,
+                                            notDuplicatable, TD);
     DEBUG(dbgs() << "  Loop Size = " << LoopSize << "\n");
+    if (notDuplicatable) {
+      DEBUG(dbgs() << "  Not unrolling loop which contains non duplicatable"
+            << " instructions.\n");
+      return false;
+    }
     if (NumInlineCandidates != 0) {
       DEBUG(dbgs() << "  Not unrolling loop with inlinable calls.\n");
       return false;